The present invention relates to a new and improved construction of an apparatus for positioning a workpiece at a machine tool, especially a horizontal drilling machine having a work spindle.
Different constructions of apparatuses for adjusting or positioning machine tool parts are known, as exemplified for instance by British Pat. Nos. 938,947, 2,000,867, French Pat. No. 772,514, U.S. Pat. No. 2,376,303 and German Pat. No. 1,247,807.
According to the invention the workpiece positioning apparatus is of the type wherein the work spindle is displaceable upon a first slide or carriage in the Y-direction, there is provided a rotatable table which is displaceable upon a second slide in the X-direction, and in the starting position of the second slide the axis of the rotatable table intersects the axis of the work spindle. Also there is provided a first measuring device for enabling rotating the rotatable table through any desired rotational angle and a second measuring device for enabling displacing the rotatable table through any desired amount in the X-direction.
It has been found that for certain tasks the aforementioned two measuring devices at horizontgal drilling machines do not fulfill the prevailing requirements. This is particularly the case if there should be produced at a workpiece a continuous bore, and part of the bore is to be produced from one side or face of the workpiece and the other part of the bore from the opposite side or face of the workpiece and both parts of the bore should be in alignment with one another. In particular, there is not ensured that with the aid of the second measuring device the slide can be displaced in such a manner into its starting position that the work spindle axis and the axis of the rotatable table do in fact intersect.
With the aforementioned two measuring devices for positioning a workpiece it is therefore not possible, without resorting to the aid of additional measuring devices, to align the aforementioned parts of the bore during the drilling operation with respect to one another such that both bore parts are in exact alignment.